1. Field of the Invention
The invention relates to the selective detection of moving objects. This may be applied for example in surveillance systems or in devices for preventing collisions with moving objects, such as in passenger cars, or for provoking such collisions, such as in missiles.
A technical requirement encountered, for example, in producing a device which must respond physically to observed moving objects, or invests a considerable amount of computation effort in an observed object, is that objects worthy of such response must be selected. Therefor, on the basis of measurements of the time development of spatial coordinates or velocity of the object, a decision must be formed whether these measurements correspond to an object which deserves further attention or not.
2. Description of the Related Art
From the prior art, criteria for such a decision are already known, for example the criterion utilized in what is called Kalman filtering, based on path prediction. Thus, in accordance with this criterion, a path model is made and on the basis of the coordinates obtained, one builds a prediction of the next coordinates, that is to say a prediction of the next point; the difference between the estimated value and the effective value of the coordinates of this point is evaluated, and thus the energy of the prediction error is measured. If this energy is low, a device can estimate the motion, that is to say it will decide that a moving object having a coherent motion is involved since it is predictable. If this energy is high, it will decide that there is an incoherent motion, as it cannot be predicted in accordance with the displacement model chosen.
However, when the case is considered in which coordinates are involved which are provided by objects of large extension, which move in a rather slow manner, or which come from a not very reliable extractor, the devices putting into effect the measurements based on the prediction do not provide good results. Actually, in the above case, the uncertainty about the measurements may be of the order of the extension of these displacements and often one is faced with what seems to be an incoherent motion made up of numerous half-turns, due to the uncertainty about the coordinates.